Double rainbow – what does it mean?

Photo: Matt Clarke

There’ve been lots of reports of rainbows and double rainbows this morning, but why do they occur?

Rainbows appear when sunlight passes through a raindrop causing it to be refracted, or bent. As the light passes through the drop, it is refracted at different angles causing the spectrum of colours from red to violet to be seen.

To see a rainbow, the sunlight needs to be behind you while a rain shower is in front of you. You can see a rainbow from a few metres to several kilometres away.

Double rainbows – sometimes called ‘rainbow hats’ – occur when a secondary rainbow forms outside of the brighter, primary rainbow. The colour sequence is reversed because the light has been reflected a second time. As the light has been refracted twice, the secondary rainbow will not be as bright.

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